Merge bitcoindevkit/bdk#1046: Avoid pinning dependencies, use --precise in ci

ffb7c795e15d2d879f2d857e7607729ca4a53155 ci: Avoid pinning dependencies, use --precise (Daniela Brozzoni)
56b8eea64330044fd7761cb2439d7dcca05106f2 ci: No need to add the llvm repository for wasm (Daniela Brozzoni)

Pull request description:

  Fixes #1035

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  evanlinjin:
    ACK ffb7c795e15d2d879f2d857e7607729ca4a53155

Tree-SHA512: a2e5e0ffea87dc86e27c2f2f3550e6e6429e66f5fd8e0196e85915de5b0f14f0e4ee9d56c87b38b101eb28d86a65868054c20421f32ecd475ca73d00471e2f8d